I recently made my first batch of mead. I Know that you should leave as little airspace as possible but all i had was 6 gallon carboys. But I made 5 gallons of mead anyway. My question is will this effect my mead significantly?
When in the fermentation process did you put it in the carboy? If it's still fermenting it shouldn't be too much of a problem, the only risk coming from the fact that more air has a greater chance of carrying undesirable microbes. I wouldn't suggest trying to bulk age it with that much head space though. It would be better to bottle it if that's the case.